In the first flush of enthusiasm that greeted the launch of the Doha development round, the end of 2004 was the deadline for wrapping things up. That was always for the birds. After the trade talks crashed and burned in Cancún, a new deadline was set - this time for the end of 2005.

That, too, was missed. But when they packed their bags at the end of the Hong Kong ministerial meeting in December, trade ministers vowed to strain every sinew to settle their differences by the end of last month. Here we are now in the second week of May and - predictably - the wrangling is still going on in Geneva.

Pascal Lamy, the director-general of the World Trade Organisation, has wisely decided not to set a fresh deadline, though he has let it be known that his 149 member governments are working against the clock. Negotiators have been told that unless they can get their act together by mid-June, they might as well give up.

Tempting though it is to assume that this is just another phoney deadline, Lamy is right to warn negotiators that they are running out of road. Looming ever larger is the only date that really matters - June 30 2007 - when President George Bush's fast-track trade negotiating powers expire and he loses the right to hand the United States Congress a WTO package on a take-it-or-leave-it basis.

The US is running a 7% trade deficit, there are mid-term elections coming up in November and protectionist sentiment is running strong on Capitol Hill. Nobody thinks for one nanosecond that Congress will agree to extend Bush's powers under the Trade Promotion Authority.

Lamy has little time for those who state that June 2007 is still more than a year away (and there is therefore no need to rush). For a start, Bush could not just plonk a trade bill in front of Congress at one minute to midnight on June 30. The legislation has to be on the Hill three months before the TPA expires.

Given the likely complexity of any deal under the Doha round, it will take time to draft the legislation, which means that the US trade negotiator would need to have a full text by the end of this year. And it will take time for the WTO to turn an outline agreement into a full text.

Clearly, the talks are now in serious trouble. There are now only two feasible outcomes: a Doha-lite deal that offers developing countries just enough to prevent them from walking away from the talks - or no deal at all. Many developing nations now believe that they stand to gain so little from the former option that they might just as well tough it out.

This is the point that Tony Blair has been making in his recent discussions with Bush, the German chancellor, Angela Merkel, and President Lula of Brazil. The prime minister says there would be a better chance of the Doha round being concluded were there more on offer. In those circumstances, he argues, countries would think twice before walking away from the negotiating table. At present, they stand to lose little by doing so. Lamy and Peter Mandelson, the European Union's trade commissioner, are held responsible for diluting the ambition of the round.

The EU certainly deserves to be fingered for helping bring about the current crisis. As the Commons development committee noted last month, Brussels could break the impasse by offering developing countries better market access in agriculture. Mandelson has not helped matters by his high-handed negotiating style, but he has to operate within a mandate set by the EU's 25 trade ministers. If they insist on continuing to protect their farmers, there is not an awful lot that Mandelson - who is instinctively as keen a free trader as Blair - can do about it.

Rather, it is up to Britain to marshal support within the EU for a more aggressive approach to the talks. The time to have done that was last December, when the Hong Kong WTO ministerial meeting coincided with the row over the future financing of the EU. Blair could have negotiated a grand bargain: Britain's rebate for a more ambitious Doha round. Instead, he let a golden opportunity slip.

In the run-up to Hong Kong, Lamy was responsible for downgrading expectations for what the meeting could achieve. Ever since, he has been badgering all the main players - the EU, US, Brazil and India - to raise the bar. The chances of success remain slim. Those close to the talks admit that they are "not pretty"; the hope is that trade ministers will take fright at the political flak that will come their way if the round collapses, and will piece something together over the next six weeks. Either way, Lamy will insist that trade ministers come to Geneva to face the music.

Ultimately, developing countries will decide the round's fate. In the past, the US has tended to push for trade rounds in response to political developments. The Kennedy round in the early 1960s, for example, was prompted by the creation of the Common Market in Europe.

This time, the US has already got what it wanted: the accession of China to the WTO. Trade comes a long way down Bush's list of worries; likewise, few in Brussels would shed many tears if the round ran into the sand.

Led by Brazil and India, developing countries are refusing to bend the knee to Washington and Brussels, as they so often have in the past. Instead, they may be tempted to play a long game, using the WTO's disputes procedure to bring the EU and US to book for $13bn (£7bn) of agricultural subsidies already deemed illegal under the Uruguay round.

In a neat analogy, Patrick Messerlin, of the Institut d'Etudes Politiques de Paris, compares the situation to pre-revolutionary France. A coalition of aristocrats - the US and EU - is confronting an increasingly impatient bourgeoisie - Brazil, China and India. This is not the time to tell them to go and eat cake.